216 ULVA. — FORPHYUA, 



II. Ulva. Linn. [Plate 25, B.] 



Frond membranaceous, of a green colour, plane, (in some 

 cases saccate, and inflated in the young state). Fnictijica- 

 tioii : imuuie (/ranules, mostly arranged in fours. — Name, 

 supposed to be from CY, water in Celtic. 



1. U. latissima, Linn. ; frond broadly-ovate or oblong, 

 flat, delicately membranaceous, of a full green colour. Grev. 

 Alij. Brit. p. 171 ; Hook. I. c. /j. 311 ; IVijatt, Alg. Danm. 

 No. 33. U. Lactucn, E. Bot. t. 1551. 



In the sea, on rocks, stones, &c., very common. Annual. All ihe year 

 round. — Fronds tiifled, 6 — 18 inches loni? or more, and several inches wide, 

 variously waved and lohed. Fructijication coverinir the whole I'roud. 



2. U- Lactnca, Linn. ; frond at first obovate, saccate, 

 inflated, at length cleft down to the base, the segments plane, 

 unequal, laciniated, semi-transparent. Grev. — Hook. I. c. p. 

 311 ; Grev. Crypt. Fl. t. 313. 



On rocks, stones, corallines, tkc. in the sea. Annual. May and June. 

 — " Fronds 3 — 6 inches in length, in the young slate obovale and saccate, 

 hut very soon burstin<j; and laceratiui^-, at length cleft irregularly to the 

 base.'' Grev. — A smaller and far more tender plant than the preceding, and 

 of a pale yellow-green colour. It adheres closely to paper in drying. 



3. U. Linza, Linn. ; frond linear-lanceolate, acute, undu- 

 late at the margin, composed of two membranes closely 

 applied. Hook. I. c.p. 311 ; fVt/att, Alg. Danm. No. 164. 



Rocks and stones in the sea. Annual. Summer. — Fronds clustered, 6 

 inches to 2 feet in length, half an inch to an inch and a half wide, linear- 

 lanceolate, tapering to each extremity, much curled, of a fine grass-green 

 colour. This species, as Dr. Greville observes, shows by its double mem- 

 brane a transition to Enteroniorpha. 



III. PoRPHYRA, Ag. [Plate 25, A.] 



Frond jjlane, exceedingly thin, and (owing to the fructifi- 

 cation) of a purple colovu*. Fruciification: 1, scattered 

 8ori of oval seeds ; 2, roundish granules, mostly arranged in 

 a quaternate manner, and covering the whole frond. Grev. — 

 Name, 7rop(piipo<;, piirjile. 



1. P. laciniata, Lightf ; fronds deeply and irregularly 

 cleft, with broad segments ; margin variously cut and lobed. 

 Grev. Alg. Brit. p. 168 ; Hook. Br. Fl. ii. p. 310 ; Harv. 



